There is a need in electronic measurement and control equipment for a precision logic controlled current split or current division circuit that provides an accurate adjustment of the relative magnitude of two currents. Current split, for example, is used in nulled-bridge type circuits, but manual adjustment is used for the current split. Other prior art circuits provided a current split of fixed magnitudes. Such known current split circuits are also not of a form that would make automatic adjustment of the amount of current split between two circuit paths readily attainable.
Programmable current source circuits are also known which use a digital to analog converter (DAC) with an operational amplifier and semiconductor switch to provide a precision single output current from a precision input voltage. Such use of a DAC is explained in a publication entitled "CMOS DAC Application Guide", Second Edition, 1984, by Phil Burton, which is available from Analog Devices, Inc. The publication does not, however, contain any current split circuits nor does it teach how any of the circuits disclosed in the publication can be modified to provide a current split circuit using a DAC.